The Neuropeptide Y (NPY) is a peptide of 36 amino acids, related to the peptide YY (PYY) and to pancreatic polypeptides (PP). Originally isolated from pig brain (Proc. Natl. Acad. Sci., 1982, 79, 5485), NPY is widely distributed in mammals at the level of the central and peripheral nervous systems. This neurotransmitter is present in high concentrations in nerve fibres of the brain, but also of the heart, the sympathetic ganglia, blood vessels and smooth muscles of the vas deferens and of the gastrointestinal tract. It is responsible for various physiological effects which are exerted via the intermediary of specific receptors (Y). The latter form a heterogeneous group, 6 sub-types of which have been identified to date: Y.sub.1 to Y.sub.6 (Pharmacological Reviews, 1998, 50, 143). NPY is involved in eating behaviour by strongly stimulating food intake (Proc. Natl. Acad. Sci., 1985, 82, 3940), or by exerting a regulatory role on the HPA (hypothalamic-pituitary-adrenal) axis (J. of Neuroendocrinol., 1995, 7, 273). It also exhibits anxiolytic and sedative properties (Neuropsychopharmacology, 1993, 8, 357), a strong vasoconstrictive ability (Eur. J. Pharmacol., 1984, 85, 519) which induces an increase in blood pressure, and also has an effect on the circadian rhythm (Neuroscience and Biobehavioral Reviews, 1995, 19, 349).
In addition to the fact that the compounds of the invention are new, they have demonstrated an in vivo inhibitory action on food intake and weight gain. That effect is exerted via the intermediary of binding to the NPY receptors. It will thus be possible to use the compounds of the invention in the treatment of pathologies in which an NPY receptor ligand is necessary, especially in the treatment of pathologies associated with eating behaviour disorders or energy balance disorders, such as diabetes, obesity, bulimia, anorexia nervosa, and also in the treatment of arterial hypertension, anxiety, depression, epilepsy sexual dysfunctions and sleep disorders.